There are three possible mechanisms of cleavage of a nitrocyclopropane radical anion 1•‾, mechanisms A (homolytic cleavage to a cyclopropyl radical 2• and a nitrite anion), B (homolytic cleavage to a distonic radical anion 3•‾ ), and C (heterolytic cleavage to a distonic radical anion 4•‾ [1]. With the models synthesized so far (Y = Z= alkyl, H = COOCH₃), only products of mechanism A have been observed [1]. On the other hand, only two cleavage mechanisms are possible for a nitrophenyl cyclopropane radical anion 5•‾, mechanisms D (homolytic cleavage to the distonic radical anion 6•‾ ) and E (heterolytic cleavage to the distonic radical anion 7•‾ ) [1]. The isolation and characterization of the products resulting from the cleavage of the nitrophenyl radical anion 5•‾ do not allow to distinguish between the two cleavage mechanisms D (homolytic cleavage) and E (heterolytic cleavage) leading to the distonic radical anions 6•‾ and 7•‾ respectively.

To shed light on the mechanisms of cleavage of those radical anions, density functional (DFT) quantum chemical calculations were carried out on species 1-3 (B3LYP 6-31+G(d), including solvation energies in acetonitrile computed using the polarizable continuum method. The results clearly favor mechanism B and species 3 over mechanisms A and C for the decomposition of anion radicals 1•‾ when Z = Y = alkyl and X = H.

[1] F. Couture-Martin, A. Sardashti, C. Cristea, J.M. Chapuzet, J. Lessard, ECS Transactions, 2008, 13, 13-19.